Coastal Wetlands Blunt Storm Impacts

Published on Monday, September 22, 2008 by The Day (Connecticut)

Wetlands-Nature’s ‘Horizontal Levees’-Blunt Storm Damage
Recent study puts a dollar value on their ability to protect coast

by Judy Benson

In 1960, Hurricane Donna taught Bob Fish a lesson he’s never forgotten.

Go to theday.com to read the complete report,

The Value of Coastal Wetlands for Hurricane Protection. Great Hammock
marsh in Old Saybrook is an example of coastal wetlands that have tangible
value in absorbing a hurricane or other major storm’s floodwaters. Go to
theday.com to read the complete report, The Value of Coastal Wetlands for
Hurricane Protection. Fish lived then on the west side of Old Saybrook
close to the Long Island Sound shoreline. As Donna’s 100-mph winds swept
through southeastern Connecticut, he recalled, the Great Hammock tidal
marsh between his neighborhood and the Sound filled quickly with waters
from the storm surge. Some roads in the neighborhood flooded, but homes
and other property were for the most part spared.

At that moment his appreciation for tidal marshes deepened, as he saw
firsthand how these wet grasslands at the shoreline can act like giant
sponges that absorb the surge. Had the marsh been filled in for
development or otherwise degraded – a fate about 30 percent of
Connecticut’s marshes fell to before laws protecting tidal wetlands took
effect in 1970 – his neighborhood would surely have had more damage.
Characterized by porous soils and regular flushing by tides and fresh
water, salt and brackish marshes were once considered wastelands but now
are valued as critical habitat for wildlife, pollution and sediment
filters and buffers against flooding.

“It’s always been one of the reasons for protecting marshes,” said Fish,
who is now chairman of the Old Saybrook Conservation Commission. “We knew
marshes were important for that reason.”

During the 1938 hurricane, which occurred 70 years ago Sunday, Great
Hammock Marsh also absorbed significant storm surge – along with some
cottages uprooted from a nearby barrier beach.

Before-and-after historical aerial photographs of the area show cottages
on an exposed barrier beach seaward of the marsh carried onto the wetlands
with the storm, noted Ron Rozsa, coastal ecologist for the state
Department of Environmental Protection. In Connecticut, he said, most
tidal wetlands sit between the uplands and a barrier beach, not right on
the shoreline.

“Barrier beaches in Connecticut take the brunt of hurricane impact,” said
Rozsa, “but we recognize that marshes also play some role in dampening the
surge.”

A new study quantifies just how much protection these wetlands provide.

In an article published in June, University of Vermont ecological
economics professor Robert Costanza and other researchers report that
their analysis of hurricane strength, property damage, property values in
vulnerable coastal areas, wetland acreage and other factors shows that
wetlands prevent an estimated $23 billion in annual damage from hurricane
winds and flooding in the Northeast and Gulf Coast. The analysis looked at
34 hurricanes from 1980 to 2004.

In Connecticut, which gets hit by a major hurricane on average once every
10 years, every 2.5 acres of coastal wetlands can be credited with
preventing about $28,500 in storm damage each year, according to the
study. It considered a little more than half of Connecticut’s 22,000 acres
of coastal wetlands to be in the zone directly affected by hurricanes.

“They have value as places to absorb floodwaters that would otherwise
accumulate elsewhere,” Costanza said in a telephone interview. “The more
wetlands a state has, the better off it’s going to be for storm damage.”

His study calls tidal wetlands “horizontal levees” maintained by nature
that are more economical and effective at damage prevention than man-made
vertical levees. They absorb storm energy, slow incoming waves and winds
and pool surge waters. This is in addition to the other significant
ecological, aesthetic and recreational values of wetlands. Restoring,
protecting, and, when possible, expanding tidal wetlands, Costanza argues,
is a highly cost-effective protection strategy for hurricane-prone areas.

“By quantifying the value of these services, it gets people’s attention,”
Costanza said. “We need to work with natural forces, not try to overpower
them.”

Connecticut restores wetlands

Thirty years ago, Connecticut began a tidal wetlands restoration program
that has brought back about 1,750 acres of degraded marshes by returning
natural tidal flows blocked by dikes, plugging ditches dug to drain or
pool water and excavating fill.

“At this point,” said Rozsa, “we’re running out of projects, because we’ve
been at this for 30 years. What’s left are the really difficult or
expensive or impossible projects.” Some of these would require moving
houses.

Still, with rising sea levels and a predicted increase in the frequency
and intensity of hurricanes from climate change, tidal wetlands could
become even more important as hurricane buffers, the study points out, so
that making investments to expand and preserve them are warranted.

“If we lose them, it will cost a lot more to replace them,” said Costanza,
the lead author of the study.

Hurricane surge maps prepared by the U.S. Army Corps of Engineers point to
some of southeastern Connecticut’s most significant marshes.

Larger marshes in the most flood-prone areas with a greater potential to
protect adjacent developed areas against flooding include the Great Island
and Upper Island complex at the mouth of the Connecticut River in Old
Lyme, the Pattagansett marsh between Black Point and Giant’s Neck in
Niantic, the Barn Island marshes in Stonington and the marshes at
Waterford Town Beach and Alewife Cove.

Statewide, about 30 percent of the coastal marshes are state-owned, while
groups like the Nature Conservancy and private owners claim others. But
the law enacted in 1970, Rozsa said, basically prohibits any activity that
would impact them.

“The tidal wetlands act has a preservation-oriented policy,” he said, “so
for all practical purposes, they are all protected.”

© 1998-2008 The Day Publishing Co.

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